• G1 phase (Gap 1) – G1 phase is the phase of the cell between mitosis and initiation of replication of the genetic material of the cell. During this phase, the cell is metabolically active and continues to grow without replicating its DNA.

• S phase (Synthesis) – DNA replication takes place during this phase. If the initial quantity of DNA in the cell is denoted as <i>2N</i>, then after replication it becomes <i>4N</i>. However the number of chromosomes does not vary, viz., if the number of chromosomes during G1 phase was <i>2n</i>, it will remain <i>2n</i> at the end of S phase. The centriole also divides into two centriole pairs in the cells which contain centriole.

• G2­ phase (Gap 2) –During this phase, the RNA, proteins, other macromolecules required for multiplication of cell organelles, spindle formation, and cell growth are produced as the cell prepares to go into the mitotic phase.

• M phase

  This is the mitotic phase or the phase of the equational division as the cell undergoes a complete reorganization to give birth to a progeny that has the same number of chromosomes as the parent cell. The other organelles are also divided equally by the process of cytokinesis which is preceded by mitotic nuclear division. The mitotic phase is divided into four overlapping stages:-

• Prophase,
• Metaphase,
• Anaphase, and
• Telophase

 Active transport is the movement of molecules across a membrane from a region of lower concentration to a region of higher concentration against the concentration gradient, often assisted by enzymes and requires energy 

 Passive transport is the movement of ions and molecules across the cell membrane without requiring energy. 

The fluid mosaic model was proposed by S.J. Singer and Garth L. Nicolson. This model explains the structure of the plasma membrane of animal cells as a mosaic of components such as phospholipids, proteins, cholesterol, and carbohydrates. These components give a fluid character to the membranes.

Each phospholipid has a hydrophilic head pointing outside and a hydrophobic tail forming the inside of the bilayer.

Cholesterol and proteins are embedded in the bilayer that gives the membrane a mosaic look. Each component has a specific function to perform.

Inclusion bodies are the non-living structures present in cytoplasm not bounded by, the membrane system. They may either lie free in cytoplasm or may be covered by 2-4 nm-thick, non-protein membrane, e.g., Vacuoles, sulphur granules, etc.

The marine animals termed echinoderms belonging to Phylum Echinodermata of Kingdom Animalia have spiny bodies. 

Characteristics of Echinodermata:

(i) Simple animals may be a star like, spherical or elongate.

(ii) Body triploblastic, coelomate, unsegmented and radially symmetrical.

(iii) Body lacks head but has oral and aboral surfaces. Oral surface of the body has five radial areas called ambulacra.

(iv) Body wall is covered with spiny hard calcareous (calcium carbonate) plates (ossicles) that forms a rigid or flexible endoskeleton.

Example: Echinus (sea urchin) and Asterias (star fish).

These classifications have a number of advantages. Following are the advantages of classifying organisms:

• It makes us aware of and gives us information regarding the diversity of plants and animals.
• It makes the study of different kinds of organisms much easier.
• It tells us about the inter-relationship among the various organisms.
• It helps to understand the evolution of organisms.
• It helps environmentalists to develop new methods of conservation of plants and animals.

Systematics is the science which deals with the diversity of organisms and their comparative and evolutionary relationships based on comparative anatomy, comparative biochemistry and physiology.

Systematics helps in

1. Providing knowledge about the evolutionary tree of life

2. Identification of new organisms

alveolar air- the amount of air present in the alvioli after insperation
inspired air- the total amont of air inspired during inspiration

Cytoplasm: It is a fluid that fills the cell and occurs between the plasma membrane and the nucleus. Cell organelles such as mitochondria, ribosomes, Golgi bodies, etc. are suspended in the cytoplasm. The cytoplasm helps in the exchange of materials between cell organelles.

Regulation of kidney function by feedback circuits: There are 2 main feedback circuit systems in the vertebrate kidneys : (i) Control by ADH and (ii) Control by JGA.
Moreover there is one extra system called ANF or atrial natriuretic factor.
(a) Control by ADH : (i) The antidiuretic hormone is secreted in the hypothalamus and released into blood by. pituitary part called neurohypophysis. It increases fluid retention by making kidney to reabsorb more water, (ii) Osmoreceptors of hypothalamus detect the osmolarity above 300 mosm L_1. The thrust is produced, (iii) Drinking of water reduces osmolarity of blood, (iv) The secretion of ADH is decreased and the circuit is completed.
(b) Control by JGA : (i) RAAS is operated by juxta glomerular apparatus, (ii) It responds to decrease in blood volume in afferent renal arterioles, (iii) The renin converts angiotensinogen I into angiotensin II which increases blood pressure and causes the arteries to constrict, (iv) In DCT and PCT there is more absorption of NaCl and water, (v) The feedback circuit is completed when the blood pressure is increased and it is supported by release of rennin.
© Control by ANF : (i) This hormone opposses the regulation of kidney7s function by RAAS. (ii) ANF is released from the walls of atria of heart response to increase in blood volume or blood pressure
(iii) ANF decreases the release of renin from JGA. So NaCl reabsorption is inhibited by CT. (iv) It reduces the release of aldosterone from adrenal. Therefore ANF, ADH and RAAS provide a system of check and balance which regulate and control body fluid osmolarity, salt concentration and blood volume or blood pressure.

Glands are important organs, you have a variety of them all over your body, and though many of them are small, each produces something important. Some glands make something that is released from the body — like saliva, sweat, or tears.  Glands are important organs located throughout the body. They produce and release substances that perform certain functions. Though you have many glands throughout your body, they fall into two types: endocrine and exocrine.

Sarcodina, the largest phylum (11,500 living species and 33,000 fossil species) of protozoans ). It comprises the amebas and related organisms; which are all solitary cells that move and capture food by means of pseudopods, flowing temporary extensions of the cell. Most sarcodines are free living; others are parasitic. Sarcodines protozoans are called Sarcodina and they move with pseudopodia. They are amoebas and are a blob of protoplasm formed in a single cell. By flowing their protoplasm forward into a "foot" then bringing the rest of their body into the foot, they can slither along.

There are four types of tissues found in animals: epithelial tissue, connective tissue, muscle tissue, and nervous tissue.

The four basic types of animal tissue are:

• Epithelial tissue is made up of layers of tightly packed cells that line the surfaces of the body for protection, secretion, and absorption. Examples of epithelial tissue include the skin, the lining of the mouth and nose, and the lining of the digestive system.
• Muscle tissue is made up of cells contain contractile filaments that move past each other and change the size of the cell. There are three types of muscle tissue: smooth muscle which is found in the inner linings of organs; skeletal muscle, which is attached to bone and moves the body; and cardiac muscle which is found only in the heart.
• Nervous tissue is made up of the nerve cells (neurons) that together form the nervous system, including the brain and spinal cord.
• Connective tissue is made up of many different types of cells that are all involved in structure and support of the body. Bone, blood, fat, and cartilage are all connective tissues. Connective tissue can be densely packed together, as bone cells are, or loosely packed, as adipose tissue (fat cells) are.

Sexual reproduction in the fungi consists of three sequential stages: plasmogamy, karyogamy, and meiosis. The diploid chromosomes are pulled apart into two daughter cells, each containing a single set of chromosomes (a haploid state). ... In most fungi the zygote is the only cell in the entire life cycle that is diploid. Sexual reproduction also occurs in virtually all fungi. This involves mating between two haploid hyphae. During mating, two haploid parent cells fuse, forming a diploid spore called a zygospore. The zygospore is genetically different from the parents.

Gregor Mendel is known as the Father of Genetics. He experimented on pea plants and discovered the basic inheritance rules.

Gregor Johann Mendel was a scientist, Augustinian friar and abbot of St. Thomas' Abbey in Brno, Margraviate of Moravia. Mendel was born in a German-speaking family in the Silesian part of the Austrian Empire and gained posthumous recognition as the founder of the modern science of genetics. Gregor Mendel, a 19th century Augustinian monk, is called the father of modern genetics.

Birds are important members of many ecosystems. They play a vital role in controlling pests, acting as pollinators, and maintaining island ecology. In addition, birds are important to humans in many ways, such as serving as a source of food and providing fertilizer in agricultural settings. Birds have feathers that help them fly. The long flight feathers on the wings and tail help birds balance and steer. In addition, birds have a system of air sacs in their body that connect to the lungs. The air sacs enable birds to extract much more oxygen from each breath of air than other animals can.

Glomerular filtration rate (GFR) is a test used to check how well the kidneys are working. Specifically, it estimates how much blood passes through the glomeruli each minute. Glomeruli are the tiny filters in the kidneys that filter waste from the blood. Angiotensin II constricts efferent arterioles, which forces blood to build up in the glomerulus, increasing glomerular pressure. The glomerular filtration rate (GFR) is thus maintained, and blood filtration can continue despite lowered overall kidney blood flow.